Unusual gases emerging from geothermal springs in Zambia’s Kafue Rift hint at the formation of deep cracks in the Earth’s crust, potentially indicating the early development of a new tectonic boundary.
Map highlighting expansion zones within Zambia’s Central African Plateau. The Kafue Rift is interconnected with the Luano and Luangwa rifts to the northeast, alongside the western branch of the East African Rift System in the Rukwa Rift (RRB) and Rungwe Volcanic Province (RVP). Image credit: Karolytė et al., doi: 10.3389/feart.2026.1799564.
Research led by Professor Mike Daly from the University of Oxford indicates that the helium isotope signature of hot springs in the Kafue Rift reveals a direct connection to the Earth’s mantle, found 40 to 160 km beneath the surface.
This fluid connection supports the notion that the Kafue Rift fault boundary is active, possibly signifying the onset of the breakup of sub-Saharan Africa and influencing the Southwest African Rift.
The Kafue Rift forms part of an extensive 2,500 km rift valley stretching from Tanzania to Namibia, extending towards the Mid-Atlantic Ridge.
Researchers focused on this area due to its unique terrain, geothermal anomalies, and numerous hot springs—indicators of a potentially undiscovered rift system.
Verifying the existence of these new fissures required evidence of cracks penetrating the Earth’s crust, allowing mantle fluids to surface.
“A fissure represents a major crack in the Earth’s crust that triggers subsidence and accompanying elastic uplift,” explained Professor Daly.
“Although a fissure can transition into a plate boundary, such activity often ceases before the lithosphere completely splits.”
Scientists investigated eight geothermal wells and hot springs in Zambia, six located within the suspected Rift Valley and two outside it.
Gas samples were collected from bubbling water and analyzed in a lab to identify the isotopic composition of each element.
Isotope testing could reveal gases originating from surface mantle fluids, providing critical insights into rifting processes.
The isotopes found in the Kafue Rift samples mirrored those from the East African Rift System, an established rift zone, while samples from outside the rift exhibited different characteristics.
Additionally, the samples revealed carbon dioxide levels consistent with gases derived from the mantle.
Helium isotopes serve as indicators of early-stage rifting. With the East African Rift System as a reference, scientists predict that carbon dioxide will become more prominent as volcanic activity intensifies over time.
“Many attributes of the Kenyan Rift Valley suggest that it could eventually serve as Africa’s primary dividing line,” added Professor Daly. “Nevertheless, the East African Rift System exhibits slow rifting.”
“Fragmentation and dispersion face challenges due to the presence of mid-ocean ridges that hinder east-west and north-south development across Africa.”
“The Southwest African Rift system presents another possibility. This rift has essential features and a regional basement structure—a natural weakness in the Earth’s crust—that aligns with surrounding mid-ocean ridges and continental topography.”
“Such alignment may lower the intensity threshold necessary for continental breakup.”
“This study primarily assesses helium data across a vast area of the Southwest African Rift Valley,” concluded Professor Daly. “Following this initial research, a broader investigation is ongoing, with results expected later this year.”
For further details, refer to the study published in the latest issue of Frontiers of Earth Science.
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Ruta Carolite et al. 2026. Southwestern Africa Rift Valley: Isotopic evidence of early continental rifting. Frontiers in Earth Science 14; doi: 10.3389/feart.2026.1799564
Source: www.sci.news
